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Fencer Vulns
high 7.5

CVE-2026-72923 json

Microsoft.OpenApi.YamlReader vulnerable to denial of service via YAML alias expansion

published 2026-09-08 2 mo ago modified 2026-10-14 25 d ago also GHSA-7pxr-59rr-hqj2 , EUVD-2026-73080

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers to extract raw OpenAPI JSON and YAML documents from the model. In Microsoft.OpenApi.Readers versions before 1.6.30 and Microsoft.OpenApi.YamlReader from 2.0.0-preview.11 through 2.11.0 and 3.0.0 through 3.9.0, parsing a YAML OpenAPI document with nested anchors and aliases can consume uncontrolled memory. SharpYaml represents aliases as shared nodes in a small directed acyclic graph, but conversion to independent OpenAPI or System.Text.Json.Nodes.JsonNode trees duplicates every aliased path; without a node-count or nesting-depth limit, N nested anchors referenced k times can require k^N materialized nodes and terminate the process through an out-of-memory condition. The fixed readers bound materialization to 5,000,000 nodes and a nesting depth of 64 by default and report an OpenApiDiagnostic error when a limit is exceeded. This vulnerability is fixed in Microsoft.OpenApi.Readers 1.6.30 and Microsoft.OpenApi.YamlReader 2.12.0 and 3.10.0.

Patch / fix

  • nuget Microsoft.OpenApi.YamlReader 2.12.0, 3.10.0
  • nuget Microsoft.OpenApi.Readers 1.6.30

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

1.85% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
nuget Microsoft.OpenApi.YamlReader
>=3.0.0, <3.10.0
>=2.0.0-preview.11, <2.12.0
3.10.0
2.12.0
nuget Microsoft.OpenApi.Readers
<1.6.30
1.6.30

Affected products

  • microsoft OpenAPI.NET

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.